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Edexcel S1 Revision Thread (09/06 09:00)

Might as well start one. =) One week left :eek:

First question: When there are outliers, do you not draw them on your box plot?

List of definitions (feel free to add)

Statistical Model - A statistical process devised to describe or make predictions about the expected behaviour of a real-world problem.

Sample space - A list of all possible outcomes of an experiment

Event - A set of outcomes of an experiment

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Reply 1

ThugzMansion7

Help! I'm stuck on Ex5a Q4e of the blue stats 1 book (heinemann)....if anyone knows, could they please draw up a venn diagram for it?

Reply 2

TheWolf

See attachment.

P(A) = 0.6
P(B) = 0.3
P(AnB) = 0.1

P(AUB') = P(A) + P(B') - P(ANB')
=0.6 +0.7 - 0.5 = 0.8

VENN.PNG12.5KB

Reply 3

ThugzMansion7

TheWolf

See attachment.

So how would I go about doing P(AuB')?

Reply 4

Chris87

Could anyone do the last 2 parts of the normal distribution question on the January 2005 paper?

jan05normaldist.gif10.4KB

Reply 5

TheWolf

c) Shaded area = 1/3 (1-0.6463) = 0.1179
d)
P(X<79+B) = 0.7642
b/12 = 0.72
b=8.64

Reply 6

Mits

TheWolf

c) Shaded area = 1/3 (1-0.6463) = 0.1179
d)
P(X<79+B) = 0.7642
b/12 = 0.72
b=8.64

Thats what I've got as well. :biggrin:

Reply 7

m:)ckel

TheWolf

First question: When there are outliers, do you not draw them on your box plot?

If they tell you to draw outliers, then draw them. Otherwise, ignore them (i.e. don't even calculate them).
Someone needs to clarify that though.

Reply 8

Mits

mockel

If they tell you to draw outliers, then draw them. Otherwise, ignore them (i.e. don't even calculate them).
Someone needs to clarify that though.

Generally if they want you to think about outliers, they will provide you with the formulae you need to calculate which items of data are outliers. If they don't mention outliers, you don't consider any items of data to be outliers so you just draw the box plot as you normally would with all data.

Reply 9

TheWolf

So if they give you outlier formulas etc, in the boxplot you draw, the smallest value would be the smallest value bar the outliers?

Reply 10

username22878

You draw crosses for where the outliers would be. So draw the box plot as normal but without any outliers included (ie the ends of the boxplot would be at the lowest and highest non-outliers) and then draw crosses where all the outliers would be.

Reply 11

TheWolf

http://math.mdsalih.com/Data/Edexcel%20Mathematics/S1/S1%20Nov%2002%20MS.pdf

Hmm The Mark Scheme's boxplot didnt show any crosses though ='(

Reply 12

peperharow

i think outliers are values that are three times the IQR above or below the max/min value.

is that right? :confused:

Reply 13

TheWolf

No, it depends on the equation given for calculating the outliers.

Reply 14

KAISER_MOLE

A definition of a statistical model would be groovy, along with conditions for particular distributions, there will be at least 4 marks on the paper asking about definitions and conditions, that is more than half a grade!
....my Statistic teacher is a complete bimbette, oh dear oh dear :P

Reply 15

TheWolf

Do you know what year the question came up? The best way is the check out the mark scheme.

Reply 16

ThugzMansion7

Could anyone help me with Ex5b Q1c, im using the P(A|B) = P(AnB)/P(B) but i can't seem to get the answer...

Reply 17

ntrik

ThugzMansion7

Could anyone help me with Ex5b Q1c, im using the P(A|B) = P(AnB)/P(B) but i can't seem to get the answer...

Lol, I got it wrong the first time as well because I didn't read the question properly. Anyway...

What they're asking for is the probability of getting red given that the first one is blue which is P(R|B).

P(R|B) = P(RnB)/P(B)

P(RnB) = 6/10 * 4/9 = 4/15
P(B) = 4/10
P(RnB)/P(B) = 2/3

Reply 18

Tindo

peperharow

i think outliers are values that are three times the IQR above or below the max/min value.

is that right? :confused:

No its depends on this: 1.5(IQR) above Q3 0r below Q1.

But they will tell you the formula anyway.

Reply 19

ntrik

When a certain type of cell is subjected to radiation, the cell may die, survive as a single cell, or divide into two cells with probabilities 1/2, 1/3, 1/6 respectively.
Two cells are independently subjected to radiation. The random variable X represents the total number of cells in existence after this experiment.

(a) Show that P(X=2) = 5/18

I can do this but I'm not sure of my approach. I drew a tree diagram displaying all possible outcomes and probabilities. Would that be sufficient to answer the question? Are there any other approaches to this type of question?